1. Field of the Invention
This invention generally relates to a bicycle hub gearbox for a multi-speed hub, for example, for a bicycle. More specifically, the present invention relates to a bicycle hub gearbox with at least a pair of planetary gear mechanisms as well as a coaster brake mechanism.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One component that has been extensively redesigned is the bicycle drive train.
Many bicycle hub assemblies include an internal power transmission mechanism having two or more power transmission paths, with each path being defined by unique gear combinations through which torque is transmitted. One example of three-speed hub gearbox with a planetary gear mechanism and a coaster brake mechanism is disclosed in European Patent Publication No. 795 461 B1. The arrangement known from this publication comprises substantially a fixed shaft, a driver, a hub sleeve, a coaster brake unit as well as a mechanism for transmission of the driving torque from the driver to the hub sleeve. The transmission mechanism comprises especially a planetary gear mechanism and a clutch arrangement, which can be actuated in a longitudinally displaceable manner and which is arranged on the driven side of the planetary gear mechanism. On the one hand, a driving torque can be transmitted in three different gear ratios through control of the clutch arrangement. On the other hand, a braking torque applied by a rider can be transmitted, such that the resulting braking force is essentially not influenced by the selected gear ratio. The interconnection of the clutch mechanism, the planetary gear mechanism and the coaster brake unit is designed for a three-speed hub.
An example a five-speed hub gearbox with a coaster brake mechanism is disclosed in European Patent Publication No. 0 383 350. This bicycle hub gearbox includes essentially a fixed shaft, a driving member, a hub sleeve, a coaster brake unit as well as a mechanism for transmission of the driving torque from the driving member to the hub sleeve. The transmission mechanism includes especially a planetary gear mechanism controllable by using sun gear clutches and a complicated clutch arrangement, arranged on the driven side of the planetary gear mechanism, whereby a driving torque can be transmitted to the hub sleeve in different gear ratios. However, it is unfavorable t hat a braking effect, which results from a braking torque applied by a rider, depends on the gear ratio selected at the time of braking. The resulting braking effect can be consequently larger or smaller than that intended by the rider.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved bicycle hub gearbox. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.